Texture slots and viewing combined textures
Simply using Material Draw Mode for combined textures is the only option in Cycles for now. Blender Render used GLSL viewport to get combined, but the nice thing about Cycles Material Draw mode is that you can toggle shadeless in the N panel without affecting the shaders themselves. Also, you might be interested in looking at BPainter addon as it simplifies and streamlines the painting experience in Blender all around.